Primary Key vs Foreign Key Explained | T-SQL Course Part 6 скачать в хорошем качестве

Primary Key vs Foreign Key Explained | T-SQL Course Part 6

In this lesson, we master the backbone of database design: Primary Keys and Foreign Keys. Without these constraints, a database is just a collection of random tables. With them, it becomes a powerful relational system. What you will learn in this tutorial: Primary Key (PK): Why every table needs one to uniquely identify a record. The Rules of PK: Understanding why Primary Keys cannot be NULL and must always be unique. Foreign Key (FK): How to link two tables (like Student and Telephone) together. Referential Integrity: Why Foreign Key values must exist in the Primary Key column first. Handling NULLs in FK: Why Foreign Keys allow NULL values (e.g., a student without a phone number) but Primary Keys do not. Data Visualization: Seeing how these keys allow us to "Join" tables to create a complete view of our data. This is a must-watch for anyone wanting to become a Database Developer or Architect! #SQLServer #DatabaseDesign #PrimaryKey #ForeignKey #TSQL #RelationalDatabase #LearnSQL #SQLConstraints